Polycarbonate resins blended with elastomers for improved impact strength

ABSTRACT

The properties, in particular the impact strength, of polycarbonate resins having an average molecular weight of at least 8000 are improved by blending such resins with from about 3 percent to about 35 percent by weight of at least one elastomer characterized by an average molecular weight ranging from about 100,000 to about 2,000,000 and a second order transition (Tg) below 0*C.

United States Patent [191 Holder et al.

[ POLYCARBONATE RESINS BLENDED WITH ELASTOMERS FOR IMPROVED IMPACTSTRENGTH [75] Inventors: Charles B. Holder; Isaac D. Rubin, both ofWappingers Falls; Carmen M. Cusano, Poughkeepsie, all of [73] Assignee:Texaco Inc., New York, NY.

[22] Filed: Jan. 7, 1971 211 App]. No.: 104,789

[52] U.S. Cl. 260/873 [51] Int. Cl. C08g 39/10 [58] Field of Search260/873 [56] References Cited FOREIGN PATENTS OR APPLICATIONS 992,5035/1965 Great Britain 260/873 OTHER PUBLICATIONS Chem. Abst. 72: 56386],Heiss; Thermoplastic Com- June 26, 1973 position.

Chem. Abst. 68: l3709s, Sakuma, Thermoplastic Components.

Chem. Abst.: 69: 3515q, Lund et al. ABS Thermoplastics.

Chem. Abst. 74: 142829d; Kato; Thermoplastic Acrylic Composition.

Primary Examiner--William H. Short Assistant ExaminerEdward WoodberryAttorney-Thomas H. Whaley and Carl G. Ries [57] ABSTRACT 5 Claims, NoDrawings 1 POLYCARBONATE RESINS BLENDED WITH ELASTOMERS FOR IMPROVEDIMPACT- STRENGTH The present invention relates to polymers. Morepartures thereof. Optimum amounts of elastomers in the blend range from5 to 20 per cent by weight. The blends of the invention are prepared inconventional manner using conventional blending equipment such asticularly, this invention is concerned with improving 5 blendel'si millsand the likey can also be the impact strength of polycarbonate resi b hat l molded in conventional fashion at temperatures usually nd at r om ter t s. ranging from about 370F. to 400F. Naturally, the it is w ll k wnto th kill d i th polymer art blends of this invention can contain anyand all desired that polycarbonate resins have high impact trengthadditives known to those skilled in this art such as flbelow a criticalthickness of between 6 and 54 inches. 10 afltlOXldantS. lubflcams, etc.Above this thickness their impact strength is low. Addi- The unexpectednature of the results obtained y the tionally, the impact strength ofpolycarbonate resins Practice of the Present mvemlon can best be PPdecreases rapidly with decreasing temperatures and med 8 the backgroundof the tabulatlons pp also after aging the polymers at elevatedtemperatures. 8 m Table 1 of P P y p fp of a lf These characteristicsconsequently limit the fields of i polycarbonatte resin, compare'd Wlthf P'Pp of application of these resins. Thus, thick polycarbonate blendsmade ,accol'dance wlth the inventioniiiiili f Heat deflect Izod impacttemp., (Lat Tensile ft. lb. per in. 26451.55 strength, Temp. Mill notchbar, de ect., Elastic p.s.i. of tests, mp., Mold 73 F. M; in. barmodulus, Percent 0. Sample F/R/ tem X At At elong. at (Izod No. )3. $2.W 0.01" 0.0 p.s.i. yield break break impact) Remarks 2.9 16.0 RIP. 1500/500 370 1.; 2.7 134.0 137.0 290.9 8,785 8,518 102 213 Polycarbonateresin (100%). 1. .8 14.8 13.3 R.T.

yearbonate resin 190 parts, butyl- 2 500/500 370 9 .4 132.5 136.5 250.27,106 7,068 49 3 g kcwlatembber, 1011mm (5%) 14.0 14.3 R.T. P01

ycarbonate resin 180 parts, butyl- 3 500/500 370 9 .2 15.; 132.5 136.0275.0 8,257 8,341 123 g harm rubber, 2013a! (10%) 15.5 13.8 R.T.Polycarbonate resin, 202.5 parts; 4 500/500 390 4.5 8.8 135.5 138.5266.5 7,182 8,209 135 ethylacrylate rubber, 22.5 parts Polycarbonateresin, 202.5 arts; 5 500 500 390 {1:3 14 132.0 137.0 254.6 7,023 7, 969123 i8 er; 22.5 parts 1 p 11.2 11.7 R.T. b t 1 a 5 500 450 400 11.1 4.2131.0 135.5 195.0 4,620 10 20 9 rubber Copolymer of 80 wt. percent butylacrylate and 20% stearyl acrylate, Tg=-70 C.

1 Butyl acrylate rubber (MW=327.00), Tg= 55 C.

bodies cannot be used where high impact strength is needed, nor at lowor high temperatures when at least good impact strength is needed.

Numerous attempts have been to remedy the above outlined shortcomings ofpolycarbonate resins but heretofore such attempts have not beensuccessful technically or from the economic standpoint.

The present invention resides in the concept of im-' proving theproperties of polycarbonate resins by incorporating therein elastomerssuch as polyacrylate rubbers,polymethacrylate rubbers, orpoly(butadieneacrylonitrile) rubbers. Unobviously and unexpectedly, itwas discovered that the incorporation of such elastomers had nodeleterious effect on the heat deflection temperature of thepolycarbonate resins when, in fact, those skilled in this art would haveexpected a significant decrease In this property upon adding to thepolycarbonate resin a material with a lowsecond order transitiontemperature. Also unexpected was the observation that the addition ofsuch rubbers only very slightly decreased the tensile properties of theresins.

In the practice of the invention, from about 3 to about percent byweight of at least one elastomer having an average molecular weight ofbetween about 100,000 and about 2,000,000 and a second order transitionbelow 0C. is blended with a polycarbonate resin having an averagemolecular weight of at least 8000. Preferred elastomers for the purposesof this invention are lower alkyl acrylate polymers and copolymers oflower alkyl acrylates with stearyl acrylates and mix- 2 Butyl acrylaterubber, Tg= -24 0.

Consideration of the data in Table 1 shows that improvements wereparticularly dramatic in the impact strength of 174 in. bars. Thus,sample 3 containing 10 wt. of a butyl acrylate rubber having a numberaverage molecular weight of 327,000 had a room temperature impactstrength of 14.3 ft. lb./in. notch, a 20 C. impact strength of 9.0 and a40 C. strength of 4.6. Substantial improvements were also obtained inthe low temperature impact strengths of the inch bars. it is clear fromthe data that all three of .the rubbers used has a beneficial effect.For best performance at low temperatures rubbers with low second ordertransitions (Tg) are preferred. This is shown by the data from thesamples 4 and 5. The rubber used in sample 5 had a Tg of about 60 to C.while that in sample 4 had one of about 24 C. The rubber with the lowerTg gave blends with better -20 Cfiand 40'C. impact strengths.

Table II below illustrates annealing data of polycarbonate resins usingpoly(methyl methacrylate) (PMMA) and poly(Neodol 25L methacrylate). Thedata given show that the second order transition (Tg) of the polymerused is very important. Thus it will be noted that PMMA, which has a Tgof C., is not effective for the. purposes of the invention.

Results substantially equivalent to those appearing above are obtainedalso when poly(butadiene acrylonitrile) rubbers are used instead ofpolyacrylate or polymethacrylate rubbers. Similar results are obtainableby using mixtures of the above rubbers.

TABLE 11 13 F. -40'r. r;

6SC. 14.4 11.5 14.2 new 6.2

are:

a. Value obtained by annealing for hra 120w,

l. Neodol 25 L methacryllte -Neodol 25b is a scmmsrcial leery! ah cohohthe methaerylate was made from it.

Polycarbonate resins (PC) have the shortcoming that their impactstrength is drastically reduced it the mate= rial is annealed below itsTg (l4QCJ, it has been shown that as little as 3 hours at 120C, cancause its impact strength to decrease from 16 to 2 .f lbrlin, notch. Thedata above given prove that the poly(butyl acrylate)- PC blend does notexhibit this behavior but rather maintains its high impact strength evenafter an= nealing for 25 hours at 120C. This heat resistance makes thecomposition of the invention useful, inter alia, in auto body componentsand appliance housings.

What is EHneETisT' l. A polycarbonate resin composition characterized byincreased impact strength and comprising a blend of polycarbonate resinhaving an average molecular weight of at least 8000 and from about 3 to35 percent by weight based on the weight of polycarbonate resin of atleast one elastomer having an average molecular weight between about100,000 and 2,000,000 with a second order transition below 0 (2 said.elas omerbeing, seleeted from the great; consisting zlower; alkyaervlategnvltnen eqnelvtner o lowe e kvl ac lv a es. with stern-v aery v .1methaerylate rubbe and Boll (methy me 2-: The semester n VQFQQQ nelaitnl qqntainlns from. f to 2Q her cent by weigh Qfisaicl elastqmen.

Q1 composition as defined ela m 1 containin 95 to 90 net sent; by weighof o l-v lrbenat res n and 5 to it) er by weight of bowl rubber hav inga number ever 8; mol lar weight; Q .;2fk,,QQQt

3, The qomnesitin as defined in. claim coma 'ning 202:5 parts of:polycarbonate and 2:21-51 par s of ethylaerylats rub/hen 5, Theeemnosition as defined claim; containing; p lyearbonat resin and 1.0 to20 per; c n parts by; eight of a copolymerof weight; per; c nt. butyljacry,-- late and 20 percen tear-yl aeryvlater E I. i *1

2. The composition as defined in claim 1 containing from 5 to 20 percent by weight of said elastomer.
 3. The composition as defined in claim1 containing 95 to 90 per cent by weight of polycarbonate resin and 5 to10 per cent by weight of butyl acrylate rubber having a number averagemolecular weight of 327,000.
 4. The composition as defined in claim 1containing 202.5 parts of polycarbonate resin and 22.5 parts ofethylacrylate rubber.
 5. The composition as defined in claim 1containing polycarbonate resin and 10 to 20 per cent parts by weight ofa copolymer of 80 weight per cent butylacrylate and 20 per cent stearylacrylate.